I. Field
The following description relates generally to wireless communications, and more particularly to confirming handoff to mitigate impact of false detection of a handoff completion signal in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple access terminals. Each access terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to access terminals, and the reverse link (or uplink) refers to the communication link from access terminals to base stations. This communication link can be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which can be referred to as spatial channels, where NS≦{NT, NR}. Each of the NS independent channels corresponds to a dimension. Moreover, MIMO systems can provide improved performance (e.g., increased spectral efficiency, higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
MIMO systems can support various duplexing techniques to divide forward and reverse link communications over a common physical medium. For instance, frequency division duplex (FDD) systems can utilize disparate frequency regions for forward and reverse link communications. Further, in time division duplex (TDD) systems, forward and reverse link communications can employ a common frequency region so that the reciprocity principle allows estimation of the forward link channel from reverse link channel.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to an access terminal. An access terminal within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, an access terminal can transmit data to the base station or another access terminal.
Handoffs oftentimes are utilized in wireless communication systems to transfer ongoing calls, data sessions, etc. from a source base station to a target base station. For instance, an access terminal can request to handoff from the source base station to the target base station. Typically, upon sending a handoff request signal to the target base station, the access terminal listens for a handoff completion signal sent from the target base station. Receipt of the handoff completion signal commonly results in the handoff to the target base station being completed. However, this technique can be susceptible to false handoff completion signal detection by the access terminal. By way of illustration, due to fading errors, physical channel errors, and so forth, when the target base station has not transmitted a handoff completion signal over the downlink, the access terminal can improperly believe such handoff completion signal was sent by the target base station.
False positive detection of the handoff completion signal can deleteriously impact overall wireless communication system performance. The access terminal can be looking for a handoff completion signal from the target base station to complete handoff when employing conventional techniques. Further, the access terminal can see a false handoff completion signal and think that handoff is complete. Moreover, the target base station has not sent a handoff completion signal and does not have knowledge of such handoff. Accordingly, the target base station is not transmitting power control commands, the access terminal is being power controlled by random power control commands (e.g., power is undergoing random: drift, . . . ) and is not being served (e.g., not receiving data packets from the target base station, . . . ). Thus, such a scenario results in loss of connectivity for the access terminal as well as interference to other users (e.g., on a reverse link channel such as a reverse link data channel, a reserve link control channel, Reverse CDMA Control Channel (R-CDCCH), . . . ).